The present invention relates generally to printers, and, in particular, to improvements in an automatic-paper-feeder portion of a printer having an automatic paper feeder incorporated therein.
Further, the present invention relates to improvements in a driving mechanism for individually feeding sheets of paper.
Still further, the present invention relates to improvements in ink jet printers, and specifically to improvements in the construction and arrangement of the print area thereof, to improvements in the construction of the mounting the ink cartridge on the carriage thereof, and to improvements for reducing the width of ink jet printers in the direction of a row.
Further, the present invention relates generally to a method of discharging paper in an ink jet printer, and, in particular, to an improved technique of the discharging paper in which the discharged paper is neither damaged nor smeared.
FIG. 56 depicts a conventional printer described in Japanese Utility Model Unexamined Publication No. 272952/1991. An automatic paper feeder is constructed and arranged having a paper feed cassette 2002, which is a paper stacker, detachably mounted in a printer body 2001 so a dead space DS is formed between the bottom of paper feed cassette 2002 and the bottom of body 2001.
FIGS. 57-59 depict a second conventional printer described in Japanese Patent Utility Model Publication No. 74825/1988 having a stacker section 2004 on which paper P is stacked, incorporated in a printer case 2003 constructed and arranged so a dead space DS is formed between the bottom of printer case 2003 and stacker section 2004.
As illustrated above, it is difficult to make the printers compact because of the dead space within the printer casings.
In the conventional printer construction of FIGS. 57-59, the stacker section is arranged as follows. If a paper discharge support 2101 rotates in a counterclockwise direction as viewed in FIGS. 58 and 59, an operating arm 2102 rotates therewith causing an intermediate lever 2103 to rotate in the clockwise direction as viewed in FIGS. 58 and 59. An engaging lever 2104 is rotated in said counterclockwise direction by the rotation of intermediate lever 2103, and a pressure-plate operating lever 2106 rotates in the same direction as engaging lever 2104 since they are both mounted for rotation with lever shaft 2105. A pressure plate member 2107 moves downward as viewed in FIG. 57 by the rotation of pressure-plate operating lever 2106 to allow paper P to be inserted between pressure plate member 2107 and a separation pawl 2108, thereby making it possible to accommodate paper P in a feeding holder 2109.
However, in such a conventional printer, if paper discharge support 2101 rotates in the counterclockwise direction, pressure plate member 2107 moves downward, but separation pawl 2108 does not move. Therefore, if a plurality of sheets of paper are inserted, the edges of the top sheets may enter above separation pawl 2108. Hence, this printer construction has a problem with the feeding-in operation.
In the above construction, intermediate lever 2103 and engaging lever 2104 are necessary, resulting in a complicated printer construction.
FIG. 60 depicts a mechanism for driving a paper feed-in roller in a conventional printer described in Japanese Utility Model Unexamined Publication No. 184174/1989. In FIG. 60, a transmission arm 2502 is supported on an apparatus body and can rotate about a fulcrum 2501. A drive gear 2503 is axially supported on fulcrum 2501. Further, a transmission gear 2505 for transmitting rotation from drive gear 2503 to a roller gear 2504 is axially supported at one side of transmission arm 2502. As a left end 2502' of transmission arm 2502 is pressed down by the movement of a carriage (not shown) against a return spring 2506, transmission gear 2505 engages roller gear 2504, and drives a paper feed-in roller (not shown) fixed on shaft 2507, which also rotatably supports roller gear 2504.
The conventional mechanism employing the structures described above has the following problem.
Since transmission arm 2502 is not resilient, if left end 2502' of transmission arm 2502 is pressed too hard by the carriage, the force of transmission gear 2505 against roller gear 2504 is too much, and gears 2504 and 2505 will not rotate smoothly.
FIGS. 61-63 depict a conventional ink jet printer described in Japanese Utility Model Unexamined Publication No. 1101980/1991. Described is an ink jet head 2201 and a paper feed roller 2202 for feeding paper P to a print area 2201a where printing is performed. A transport roller 2203, roller 2202 which is disposed downstream of paper feed roller 2202 relative to print area 2201a, rotates at a higher peripheral speed than paper feed roller 2202 and pulls paper P past paper feed roller 2202. A paper holding plate 2204 holds paper P against paper feed roller 2202. In a printer having the above construction, paper P is printed in print area 2201a while paper P floats.
However, with this type of printer, "blind striking" may occur in which ink is ejected from ink jet head 2201 despite the fact there is no paper P in print area 2201a.
Blind striking occurs after the paper is detected by a paper detecting sensor disposed upstream of the print area but the paper fails to reach the print area due to a failure in paper feed, or the like. If the paper is detected by the paper detecting sensor, ink jet head 2201 operates on the assumption that the paper is present in the print area.
As shown in FIGS. 61-63, because there is nothing interposed between ink jet head 2201 and paper feed roller 2202, when "blind striking" occurs, the ink ejected from ink jet head 2201 adheres to paper feed roller 2202, thereby staining later sheets of paper P. This has been a serious problem with conventional printers having this construction.
Furthermore, a distal end of paper holding plate 2204 in the conventional printer shown in FIGS. 61-63 functions to restrict the printing surface of the paper P. As noted above, in this conventional printer paper holding plate 2204 presses paper P paper feed roller 2202. However, with inherent surface irregularities in paper feed roller 2202, paper holding plate 2204 is pivotably displaced due to the effect of these irregularities and the pressure exerted on paper P by paper holding plate 2204 varies. This results in the gap between the printing surface and ink jet head 2201 varying, which adversely affects the print quality. In addition, since a plurality of paper holding plates 2204 are provided in the axial direction of paper feed roller 2202, as shown in FIG. 61, paper holding plates 2204 are affected by the surface irregularities of paper feed roller 2202 at different locations in the axial direction thereof, and will pivot at different angles and at different instances, which will also adversely affect the print quality.
Further, ink jet printers print by discharging ink onto paper. If the printed paper is discharged by means of, for instance, a pair of rubber rollers, the ink that is not dry will adhere to the rubber rollers on the printed surface side, thereby smearing the ink on the printed surface of the paper.
Accordingly, FIG. 64 illustrates an ink jet printer described in Japanese Utility Model Unexamined Publication No. 41277/1990 that has been proposed to overcome this problem. Paper P1, printed on by an ink jet head H, is discharged using a paper discharge roller 2401 made of a resilient material, such as rubber, and a plurality of star wheels 2402 which rotate with the paper nipped between star wheels 2402 and paper discharge roller 2401. Star wheels 2402 are urged toward paper discharge roller 2401 by means of respective shafts 2403 each having a resiliency or spring characteristic.
However, the conventional printer employing the structure described above has the following problem.
Star wheels 2402 are urged toward paper discharge roller 2401 by shafts 2403 each having a spring characteristic. If there are variations in the spring characteristic (i.e., on the urging force) of shafts 2403, the variations appear directly as variations in the pressing force of star wheels 2402 upon paper discharge roller 2401.
If the pressing force of star wheel 2402 upon paper discharge roller 2401 is small, it becomes impossible to obtain a transporting force for the paper. Conversely, if the pressing force is too large, perforations can form in the paper, and the printed surface, therefore, is liable to be damaged.
Since the ink jet printer prints onto paper by the ejection of ink, when printing is performed continuously on a plurality of sheets of paper, a subsequent sheet of paper may be discharged before the ink on the printed paper dries. If the subsequent sheet of paper contacts the preceding sheet of paper, the ink on the printed surface will smear.
Japanese Utility Model Unexamined Publication No. 134865/1992 describes a discharged paper stacker that overcomes this problem. The construction thereof is described with reference to FIGS. 65-68. FIG. 65 illustrates a discharged-paper tray 2306 having a V-shape or concave shape. FIG. 66 shows how printed sheets of paper P1 are stacked in the concave shape thereby delaying the time until subsequently discharged paper P2 contacts printer paper P1. In addition, FIG. 67 illustrates a technique in which paper P2 is discharged and is set in a convex shape to delay the time until paper P2 slidably contacts printed paper P1. In this arrangement, central interior roller 2304' is of a larger diameter than outer interior rollers 2304 while central exterior roller 2305' is of smaller diameter than outer exterior rollers 2305. Furthermore, FIG. 68 describes a technique in which paper P2 is discharged and is set in a corrugated shape to further delay the time until paper P2 contacts printed paper P1. In this construction, interior rollers 2304" have projecting peripheral hubs while exterior rollers 2305" are thin and aligned with the central region of interior rollers 2304" between the hubs.
However, these conventional techniques employing the structures described above have the following problems.
First, even if discharged-paper tray 2306 is formed in a concave shape, if paper P1 is very stiff, paper P1 will not conform and stack in the desired concave shape. As a result, the time until subsequently discharged paper P2 slidably contacts printed paper P1 is not delayed, and the printed surface of printed paper P1 will smear. Also, because the shape of discharged-paper tray 2306 is concave, the space occupied by discharged-paper tray is larger than desired.
Furthermore, the print quality utilizing the techniques shown in FIGS. 67 and 68 is poor. Paper discharge rollers 2304 and 2305 cause paper P2 to be set directly in the convex shape or in the corrugated shape. This results in paper P2 retaining the aforesaid shapes while in the printing section, thereby adversely affecting the print quality.
Ink jet printers having an ink cartridge mounted on a carriage have heretofore been proposed. These printers are more compact than a printer not having the ink cartridge mounted on the carriage and where ink is supplied to the ink jet head located above the carriage through a pipe from an ink tank.
Japanese Utility Model Unexamined Publication No. 101949/1991 describes a printer in which the operation of mounting or demounting of the ink cartridge with respect to the carriage can be performed simply by the operation of a lever.
However, this type of conventional printer is constructed and arranged so that the carriage can reciprocate even in a case where the operation of mounting the ink cartridge has not been performed completely.
For this reason, in the event that the carriage reciprocates in the state in which the mounting of the ink cartridge has been performed incompletely, there is the possibility of the ink cartridge coming off the carriage, thereby possibly staining paper or the path of the paper in the printer.
In addition, since no shock-absorbing member is interposed between the carriage and the ink cartridge, when the carriage suddenly reverses direction, any inertial force of the ink cartridge is directly transmitted to the carriage, causing vibrations to the carriage and excess noise.
Ink jet printers generally have a print area where printing is performed on recording paper by the head mounted on the carriage which reciprocates in the direction of a row, and a nonprint area located outside the print area where printing is not performed. In such ink jet printers, if printing is not performed for a predetermined time, the ink at the tip of the nozzle of the head becomes dry, and causes the nozzle to clog. To prevent this, it is necessary to perform a so-called "capping" operation and cover the ink jet head with a cap. However, if clogging has occurred, it is necessary to clear the ink path by forcibly sucking the ink from the nozzle using a sucking mechanism. The capping and sucking operations are performed when the carriage is in the nonprint area. Further, when the printing operation is continuously performed, the paper is fed for the portion of the interlinear space when the carriage is in the print area.
The driving for paper feed and the driving of the suction mechanism are conventionally performed by separate drive motors although printers in which the driving of the respective mechanisms is performed by one drive motor have become popular in recent years.
FIGS. 69-71 are schematic diagrams respectively illustrating the print area and the nonprint area in different types of conventional ink jet printers with the frame of the printer indicated as F.
FIG. 69 describes an ink jet printer having nonprint areas a1 and a2 on both sides of a print area P. When the carriage is in nonprint area a1, the paper feeding-in operation and the paper feeding operation are performed. When the carriage is in nonprint area a2, the capping operation is performed. Also, when the carriage is in nonprint area a2, the paper feeding operation and the suction operation are performed simultaneously.
FIG. 70 describes an ink jet printer having three nonprint areas a1, a2, and a3 on one side of print area P. When the carriage is in print area P and a first nonprint area a1, the paper feeding operation is performed. When the carriage is in nonprint area a2, the paper feeding-in operation is performed. When the carriage is in nonprint area a3, the suction operation is performed. In addition, the capping operation is performed when the carriage is in any one of the nonprint areas a1, a2, and a3.
Similarly, the ink jet printer shown in FIG. 71 has three nonprint areas a1, a2, and a3 on one side of the print area P. When the carriage is in the first nonprint area a1, the paper feeding-in operation is performed. When the carriage is in nonprint area a2, the paper discharging operation is performed. When the carriage is in nonprint area a3, the suction operation is performed. In addition, the paper feeding operation is performed when the carriage is in any one of the nonprint areas a1, a2, and a3.
The conventional ink jet printers employing the structures described above have the following problems.
As illustrated in FIG. 69, only two nonprint areas are provided for the ink jet printer so the width of the printer in the direction of the row can be made small. Nevertheless, since both the paper feeding operation and the suction operation are performed simultaneously in nonprint area a2, a problem arises when the recording paper is continuously fed during the suction operation. Particularly, in a case where the recording paper is continuous-form paper, the recording paper is fed by the portion in which the suction operation was performed, which is very inconvenient. In addition, if the paper feeding operation is performed in a state in which capping is provided, the suction operation is performed even if the head is not clogged, resulting in wasted ink.
The ink jet printer shown in FIG. 70 does not have the above-mentioned problems, but, since there are as many as three nonprint areas, the width of the printer in the direction of the row becomes large.
The ink jet printer shown in FIG. 71 is also provided with three nonprint areas, so the width of the printer in the direction of the row is large. Moreover, since both the paper feeding operation and the suction operation are performed simultaneously in nonprint area a3, a problem similar to that of the printer shown in FIG. 69 will result.
By the arrangement in accordance with the invention, the foregoing deficiencies in the prior art are overcome. Specifically, a compact printer is provided. The printer paper feed mechanism permits an accurate feed-in operation with a simple mechanism which prevents the paper's insertion above the separation pawl. Further, the smooth operation of the mechanism for driving the feed-in roller is assured. The ink jet printer in accordance with the invention is designed so that the paper is not stained even if blind striking occurs and to keep constant the gap between the printing surface of the paper and the head. Further, the ink jet printer transports paper reliably without staining the printed surface by, at least in part, delaying the time until paper which is discharged next is brought into sliding contact with the printed paper, while preventing the configuration of the paper from affecting the printing section. Still further, means is provided to prevent the ink cartridge from coming off the carriage. The cartridge mounting mechanism is adapted to reduce vibration and noise. Still further, the width in the direction of the row for ink jet printer is reduced while the paper feeding and suction operations are selectively effected.